Zeroth law of thermodynamics
Zeroth is one of the fourth laws of thermodynamics. It was
formulated by Ralph H. Fowler.
Definition of Zeroth law of thermodynamics:
Zeroth law of thermodynamics states:
“ If two thermodynamics systems
are each in thermal equilibrium with a third system, then those first two
systems are in thermal equilibrium with each other.”
Before going deep into the concept we need to know some
terms which are necessary to know.
Thermal equilibrium:
If the object is at constant temperature and maintains it
then it is said to be thermal equilibrium. For example, when a higher
temperature object is in contact with a lower temperature, the object will
transfer heat to the lower temperature object. Then, the object will approach
the same temperature, they will then maintain a constant temperature. They are
then said to be in thermal equilibrium
Examples:
·
When we place the food in the refrigerator,
after some time the food reaches the thermal equilibrium state with the
refrigerator.
·
When two cups of tea one are hotter than the
another is placed on the table and left for some time. After some both attain
the state of thermal equilibrium with the temperature of the room.
Applications of zeroth law of thermodynamics:
This law is important and has applications in many fields of
science. The main applications of the zeroth law of thermodynamics are
The zeroth law of thermodynamics is important for the
mathematical formulation of thermodynamics
This law is used to compare the temperature of different
bodies.
This law is used to state the definition of temperature.
It is used to measure the temperature of the system, body,
etc. For example The we want to measure
the temperature of the room, them some reference which containing some specific
charter times are required. These specific characteristics are known as
thermodynamic properties. The change in characteristics is known as the
indication of the temperature change.
Another common application of the zeroth law of
thermodynamics is seen in thermometers. This can be observed by taking the
example of the simple thermometer with mercury in it. Mercury expands when the
temperature increase due to this the height is increased. The change in height shows
us that the temperature changes and helps to measure it.
There is some thermometer used depending upon the thermometric
property. They are as follows
|
Thermometer |
Thermodynamics
property |
|
Constant volume
gas thermometer |
Pressure |
|
Constant
pressure gas thermometer |
volume |
|
Electrical
resistance thermometer |
resistance |
|
Thermocouple |
Thermal emf |
|
Mercury – in
glass thermometer |
length |
History postulates of zeroth law:
Sommerfeld and Fowled concluded the statement of the zeroth
law of thermodynamics. While Meghnad Saha and B.N. Srivastava gave some
statements which refer to the zeroth law of thermodynamics, these are;
·
Every physical quantity must be measurable in
physical terms.
·
Any of the physical properties of A which
changes with heat may be observed and utilize for the measurement of the
system.
·
If body A
is in temperature equilibrium with two bodies B and C, then B and C will
be in thermal equilibrium with each other.
Fowler and Guggenheim ( 1936/ 1965) wrote of the zeroth law as follows;
·
If two assemblies are each in thermal
equilibrium with a third assembly, then are in thermal equilibrium with each
other.
The postulate of “ Existence of the Temperature” could with
advantage also known as zeroth law of thermodynamics.
Zeroth law as Equivalence
relation:
The relation of
zeroth law is an equivalence relation on the pairs of thermodynamics systems.
In other words, it can be said that all the systems with their internal thermodynamics
equilibrium may be divided into subsets where any member of the set is a member
of one and only one such subset.
some relations of this are
reflexive relation: when the thermodynamics system is
in thermal equilibrium with its self then it is called reflexive relation.
Binary relation: If two system is in thermal
equilibrium with a third system, then there are in thermal equilibrium with
each other, then they are said to be in a binary relationship.
Transitive relation: if A is in thermal equilibrium
with B and if B is in thermal equilibrium with C, then A is in thermal
equilibrium with C, then these are said to be transitive relations.
Ideal gas thermometer:
For ideal gas there are most commonly three parameters are
used these are pressure P, volume V, and numbers of moles N. If two systems of
ideal gases are joint in thermal equilibrium across the diathermal wall. Then,
P1V1/N1=P2V2/N2
The system PV/N=constant defines a system of equal
thermodynamic temperature. It may also write as PV/N=RT, where R is constant
and T is the temperature. This system can be used to collaborate with others.
This is called an ideal gas thermometer.
Limitation of the zeroth law of thermodynamics:
The zeroth law provides no information regarding the final
state of the system. For example, if two systems are in different thermal
equilibrium states measured by the ideal thermometer. If we thermal connect
these two systems then, after some time if we measure both systems by
thermometer there is no difference between them, they both are reached at the same
state. This is the limitation of the zeroth law of thermodynamics it does not
tell us about the final state of the system.
This is dummy text. It is not meant to be read. Accordingly, it is difficult to figure out when to end it. But then, this is dummy text. It is not meant to be read. Period.
ConversionConversion EmoticonEmoticon